OFFSET
0,2
COMMENTS
sigma(n,k) denotes the sum of the k-th powers of the divisors of n.
LINKS
Michel Marcus, Table of n, a(n) for n = 0..100
FORMULA
After initial term, equals the logarithmic derivative of A156360.
Conjecture: a(n) = A023887(n)*((2^n - 1)/(2^(n*(A007814(n) + 1)) - 1) + 2^n) for n > 0. - Velin Yanev, Jul 08 2017
a(n) ~ (2*n)^n. - Vaclav Kotesovec, Aug 21 2017
MATHEMATICA
Table[If[n == 0, 1, DivisorSigma[n, 2 n]], {n, 0, 15}] (* Michael De Vlieger, Jul 12 2017 *)
PROG
(PARI) a(n)=if(n==0, 1, sigma(2*n, n))
(Python)
from sympy import divisor_sigma
def A179504(n): return divisor_sigma(n<<1, n) if n else 1 # Chai Wah Wu, Jul 08 2022
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Sep 21 2010
STATUS
approved